現在從上一章延伸，補上缺少的部分，完成整個安全流程。

## 取得 `username` 與 `password` { #get-the-username-and-password }

我們要使用 **FastAPI** 提供的安全性工具來取得 `username` 與 `password`。

OAuth2 規範中，當使用「password flow」（我們現在使用的）時，用戶端／使用者必須以表單資料送出 `username` 與 `password` 欄位。

而且規範要求欄位名稱必須就是這兩個，所以像是 `user-name` 或 `email` 都不行。

但別擔心，你在前端要怎麼呈現給最終使用者都可以。

而你的資料庫模型也可以使用任何你想要的欄位名稱。

  /** Use high bits of metadata for modification count. */
  static final int MODIFICATION_COUNT_INCREMENT = 1 << HASH_TABLE_BITS_MAX_BITS;

  /** Bitmask that selects the low bits of metadata to get hashTableBits. */
  static final int HASH_TABLE_BITS_MASK = (1 << HASH_TABLE_BITS_MAX_BITS) - 1;

  /** Maximum size of a compact hash-based collection (2^30 - 1 because 0 is UNSET). */

Dieses *Pfadoperation*-spezifische OpenAPI-Schema wird normalerweise automatisch von **FastAPI** generiert, Sie können es aber auch erweitern.

/// tip | Tipp

Dies ist ein Low-Level-Erweiterungspunkt.

Wenn Sie nur zusätzliche Responses deklarieren müssen, können Sie dies bequemer mit [Zusätzliche Responses in OpenAPI](additional-responses.md) tun.

///

#### Declaring tasks

The elasticsearch build makes use of the [task avoidance API](https://docs.gradle.org/current/userguide/task_configuration_avoidance.html) to keep the configuration time of the build low.

When declaring tasks (in build scripts or custom plugins) this means that we want to _register_ a task like:

    tasks.register('someTask') { ... }

instead of eagerly _creating_ the task:

        .withFeatures(features)
        .suppressing(parentBuilder.getSuppressedTests())
        .createTestSuite();
  }

  /**
   * Returns an array of four bogus elements that will always be too high or too low for the
   * display. This includes two values for each extreme.
   *
   * <p>This method (dangerously) assume that the strings {@code "!! a"} and {@code "~~ z"} will

    boolean set(long bitIndex) {
      if (get(bitIndex)) {
        return false;
      }

      int longIndex = (int) (bitIndex >>> LONG_ADDRESSABLE_BITS);
      long mask = 1L << bitIndex; // only cares about low 6 bits of bitIndex

      long oldValue;
      long newValue;
      do {
        oldValue = data.get(longIndex);
        newValue = oldValue | mask;
        if (oldValue == newValue) {

        assertEquals((byte) 0xFF, buf[1], "AndX command should be 0xFF when no chaining");
        assertEquals((byte) 0x00, buf[2], "Reserved byte must be 0");
        assertEquals((byte) 0xDE, buf[3], "Sentinel low offset when no chaining");
        assertEquals((byte) 0xDE, buf[4], "Sentinel high offset when no chaining");
        assertNull(block.andx, "andx should be cleared when not chaining");
    }

    @Test

  // TF eager runtime.
  // TODO(b/172877902): These helper functions are currently used to support
  // PyFuncOp on TFRT, and might be useful for ops that directly use low
  // level TF APIs. Remove/replace the following functions when TFRT native
  // ops are implemented.
  //===--------------------------------------------------------------------===//

Puede ser utilizada por aplicaciones y sistemas de terceros.

Y también puede ser utilizada por ti mismo, para depurar, revisar y probar la misma aplicación.

## El flujo `password` { #the-password-flow }

Ahora retrocedamos un poco y entendamos qué es todo eso.

El "flujo" `password` es una de las formas ("flujos") definidas en OAuth2, para manejar la seguridad y la autenticación.

Pode ser usada por aplicações e sistemas de terceiros.

E também pode ser usada por você mesmo, para depurar, verificar e testar a mesma aplicação.

## O fluxo de `password` { #the-password-flow }

Agora vamos voltar um pouco e entender o que é isso tudo.

O "fluxo" `password` é uma das formas ("fluxos") definidas no OAuth2 para lidar com segurança e autenticação.